8 
CHANGES IN BLOOD BY REPEATED BLEEDINGS. 
Bilt, from Dr. Prout’s experiments, (Annals 
of Philosophy, II., 328; and IV.,331,)it ap- 
pears that the quantity of carbonic acid gas 
produced by respiration, is at its maximum at 
noon, and tba' its quantity at 1 1 A. M. is to the 
mean quantity for 2 1 hours, as 3-92 to 315. It 
is obvious, from this, that the meab volume of 
carbonic acid gas in lt)0 volumes of air expired, 
deduced from the preceding experiments, 
is 3-72. 
1 made a few trials to to ascertain how mncli 
air ditlerent individuals are capable of forcing 
out of their lungs after a full inspiration. The 
quantity as might be expected, varies much 
in different individuals. But when the same 
individual re neated the trial .the result was very 
constantly the same. The following table 
shows the results. — 
Mr. T. Thomson, 1.50, cubic inclie.s. Mi’. 
G. Thomson, 1G3, Dr. Duncan, 180, Dr. Thom- 
son 193, Mr..! Colquhoun 2011, jMr. Coverdale 
200, Mr. Bruce 2()0, Mr.. Forrest, 200, Mr. 
Frazer, 200, Dr. Short, 210, Mr. Cargill 2 )0, 
200 cubic inches is the most common quanti- 
ty ; but in one case it amounted to as much as 
2,50. 
The number of respirations in a minute 
does not vary much in different individuals, 
being very nearly twenty, or rather between 
nineteen and twenty, 
I believe that great errors have been com- 
mitted ill the attempts to determine the quan- 
tity ofair thrown out of the lungs by a com- 
mon expiration. I am satisfied that the quan - 
tity which I pitched upon from the experi- 
ments of Menzies, Lavoisier, &c., namely, 
forty cubic inches is far too high. 1 find, 
after a great many trials, (for it is very dilli- 
cult to make a natural expiration when your 
attention is called to’ it,) that the quantity of 
air which I myself throw out at a natural ex- 
piration, is sixteen cubic inches. My nephew. 
Dr. Andrew Steel, who w'as a tall man, 
(about six feet,) with an expanded chest, also 
made many trials, and satisfied himself that 
his ordinary expiration was sixteen cubic 
inches. Messrs. Allen and Pepys deter- 
mined the volume ofair expired by them at an 
ordinary expiration, to be sixteen and a half 
cubic inches. From these facts, I think we 
are entitled to conclude that a common ex- 
piration does not much exceed sixteen cubic 
inches. 
If these data be correct, and they cannot be 
very far from the truth, it will be ^"ery easy 
to calculate the quantity of carbon thro\vn out 
of the body daily by respiration. Allowing 
20 respirations per minute, and IG cubic inches 
of air taken in and thrown out at each respi- 
ration, we liave 28,800 respirations in 21 
hours, and 460,800 cubic inches ' f air passing 
through the lungs. Of this or 17141-76 
cubic inches are converted into carbonic acid 
gas. Now OO cubic inches of carbonic acid 
weigh very nearly 50 grains : so that the 
weight of carbonic acid formed is 8,570.8 
grains, -j^^ths of which, or 2337.5 grains are 
caibon. This amounts to nearly nine ounces 
avoirdupois, or somewhat more than half a 
pound , — Record of Science, 1835. 
ON THE CHANGES PRODUCED IN 
THECOVIPOSION OF THE BLOOD 
BY REPEATED BLEEDINGS. 
By Thomas Andrews, Esq. 
The objectofthe following experiments is to 
determine with precision, the changes which 
are produced in the composition of the blood 
by re[)eated abstractions of large quantities of 
it from the general circulation. In the human 
subject, oiiportunities seldom occur of procu- 
ring proper specimens for examination, al- 
though the operation of vene, section is so fre- 
quently performed, as in those cases where 
it requires to be repeated at short intervals 
the blood is generally in a morbid state. In- 
stead of waiting for such casual occasions, I 
directed my attention to those animals in 
which the composition of the blood is nearly 
the same as in man, conceiving that similar 
results would in either case be produced. I 
selected the blood of calves for the fuirpose 
of experiment, and as it is the practice of 
butchers in this country to bleed these ani- 
mals several times before they are slaughtered, 
I availed myself of this circumstance to, pro- 
cure suitable portions of blood- The animal 
is bled from a large orifice in the jugular vein, 
till symptoms of syncope apiiear, and the 
operation is in general repeated at intervals of 
twenty four hours It is once fed between 
each operation upon a mixture of meal and 
water, but this is often omitted before the last 
bleeding. 
The appearance of the blood becomes great- 
ly altered by the successive abstractions ; the 
crasamentum is at first very large, and a por- 
tion of the red globules are unattached to it, 
but it progressively diminishes in bulk while 
its con.sistency increases, till upon the fourth 
bleeding it appears a small contracted ball im- 
mersed in a large quantity of serum, adher- 
ing to the stopper of the vessel in Avhich it is 
contained, and presenting on its external sur- 
face an exact cast of the interior of the vessel . 
The following analyses were performed by 
the same method that I formerly employed in 
a set of experiments on the blood of cholera 
patients, which were published in the Philo- 
sophical Magazine for September, 1832. They 
are nearly alia mean of two separate analyses 
which seldom differed from each other more 
than 0-5 per cent, 
A calf was bled four times ; between the 
first and second bleedings a week elapsed, 
but the rest took place at intervals of twenty- 
four hours, and the animal' was fed between 
each operation. The composition of tlie serum 
and blood at each bleeding is exhibited in the 
following tables : 
SERUai. 
Water 
Albumen 
and Salts 
I'IRST. 1 SECOND. 1 THIRD, j 
FOU RTH 
92-19 
7.82 
93-96 
6.04 
93-81 
6.19 
“oiTTs 
5.82 
100.00 
100.00 
100.00 
100.00 
